Air-cooled ammonia refrigeration systems and methods

ABSTRACT

In some embodiments, an air-cooled ammonia refrigeration system comprises: an air-cooled condenser comprising a heat exchanger and at least one axial fan; an evaporator coupled to the air-cooled condenser; a subcooler positioned between the air-cooled condenser and the evaporator; a compressor coupled to the evaporator; an oil cooler coupled to the compressor; a water system coupled to the air-cooled condenser, the water system comprising a water source, a water pump, and a plurality of spray nozzles positioned below the air-cooled condenser; and a control circuit coupled to the air-cooled condenser and the water system, the control circuit configured to pulse atomized water through the plurality of spray nozzles to a surface of the air-cooled condenser when a head pressure of the air-cooled condenser is higher than a predetermined value.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/649,742 filed on Jul. 14, 2017, now U.S. Pat. No. 10,670,307, whichclaims the benefit of U.S. Provisional Application No. 62/363,151 filedon Jul. 15, 2016, each of which are incorporated herein by reference intheir entireties.

TECHNICAL FIELD

This invention relates generally to the use of an air-cooled condenserin an ammonia refrigeration system.

BACKGROUND

Various large-scale industrial refrigeration systems are known in theart. One approach to large-scale industrial refrigeration systemsessentially comprises the use of an evaporative condenser in combinationwith ammonia (NH3) as a refrigerant. In such a system, the heatexchanger is continuously sprayed with water, which removes heat fromthe circulating vaporous ammonia in the heat exchanger to form liquidammonia. Evaporative condensers require large amounts of water, whichcan be costly to source, especially in geographic areas that are arid orareas that may be suffering from drought. Additionally, the use ofevaporative condensers can often result in large amounts of wastewater,which can be costly to treat and/or dispose of. Accordingly, it can beadvantageous to improve refrigeration systems to reduce energy, water,and wastewater costs.

BRIEF DESCRIPTION OF THE DRAWINGS

Disclosed herein are embodiments of systems, apparatuses and methodspertaining to air-cooled ammonia refrigeration systems. This descriptionincludes drawings, wherein:

FIG. 1 illustrates a simplified block diagram of an exemplary air-cooledammonia refrigeration system in accordance with some embodiments.

FIG. 2 illustrates a simplified block diagram of an exemplary air-cooledammonia refrigeration system in accordance with some embodiments.

FIG. 3 illustrates a simplified diagram of an exemplary air-cooledcondenser in accordance with some embodiments.

FIG. 4 illustrates a simplified diagram of an exemplary air-cooledcondenser in accordance with some embodiments.

FIG. 5 illustrates a simplified diagram of exemplary elevated air-cooledcondensers in accordance with some embodiments.

FIG. 6 illustrates a simplified flow diagram of an exemplary process ofproviding refrigeration using an air-cooled ammonia refrigerationsystem, in accordance with some embodiments.

FIG. 7 illustrates an exemplary system for use in implementing systems,apparatuses, devices, methods, techniques and the like in using anair-cooled condenser in an ammonia refrigeration system in accordancewith some embodiments.

Elements in the figures are illustrated for simplicity and clarity andhave not necessarily been drawn to scale. For example, the dimensionsand/or relative positioning of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding of various embodiments of the present invention. Also,common but well-understood elements that are useful or necessary in acommercially feasible embodiment are often not depicted in order tofacilitate a less obstructed view of these various embodiments of thepresent invention. Certain actions and/or steps may be described ordepicted in a particular order of occurrence while those skilled in theart will understand that such specificity with respect to sequence isnot actually required. The terms and expressions used herein have theordinary technical meaning as is accorded to such terms and expressionsby persons skilled in the technical field as set forth above exceptwhere different specific meanings have otherwise been set forth herein.

DETAILED DESCRIPTION

The following description is not to be taken in a limiting sense, but ismade merely for the purpose of describing the general principles ofexemplary embodiments. Reference throughout this specification to “oneembodiment,” “an embodiment,” “some embodiments”, “an implementation”,“some implementations”, “some applications”, or similar language meansthat a particular feature, structure, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe present invention. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” “in some embodiments”, “in someimplementations”, and similar language throughout this specificationmay, but do not necessarily, all refer to the same embodiment.

Generally speaking, pursuant to various embodiments, systems,apparatuses and methods are provided herein for using an air-cooledcondenser in an ammonia refrigeration system. The system includes anair-cooled condenser, which is sometimes referred to as a “waterlesscondenser” because it does not require the use of water to condense therefrigerant as is used in an evaporative condenser. The air-cooledcondenser comprises a heat exchanger and at least one axial fan, theair-cooled condenser being configured to condense vaporous ammonia toform liquid ammonia. The system further includes an evaporator coupledto the air-cooled condenser and configured to evaporate liquid ammoniareceived from the air-cooled condenser to form vaporous ammonia, and asubcooler positioned between the air-cooled condenser and theevaporator, the subcooler being configured to remove heat from theliquid ammonia passing from the air-cooled condenser to the evaporator.A compressor is coupled to the evaporator and configured to compress thevaporous ammonia received from the evaporator, and an oil cooler coupledto the compressor and configured to remove heat from circulating oil inthe compressor.

Although the air-cooled condenser used in the system described herein isgenerally referred to as a “waterless condenser,” in some embodiments,the system may also include a water system coupled to the air-cooledcondenser, the water system comprising a water source, a water pump, anda plurality of spray nozzles positioned below the air-cooled condenser.The water system may be used to control the head pressure of theair-cooled condenser via a control circuit coupled to the air-cooledcondenser and the water system. With air-cooled condensers, highlyvariable ambient temperatures and/or large variations in the systemload, can result in head pressures that are insufficient to ensureadequate flow of the refrigerant through the system. Accordingly, in thesystem described herein, the control circuit may pulse atomized waterthrough the plurality of spray nozzles to a surface of the air-cooledcondenser when a head pressure of the air-cooled condenser is higherthan a predetermined value. Uniquely, the water system is configured tointermittently spray water to control the head pressure of theair-cooled condenser, and not in response to a detected temperature. Insome embodiments, the control circuit pulses the atomized water suchthat the atomized water evaporates upon contact with the surface of theair-cooled condenser. In some embodiments, the atomized water maycontain a water softening agent.

The system described herein surprisingly allows for the use of ammoniarefrigeration in a configuration that increases efficiency and reducesoperating costs compared to previous ammonia refrigeration systems.Previously, evaporative condensers were used in ammonia refrigerationsystems. In a typical evaporative condenser refrigeration system, wateris continuously sprayed over the condensing coil from above, which isusually made of galvanized steel, while air is simultaneously blown upthrough the coil from below to lower the condensing temperature. Theamount of water used to spray the coils of an evaporative condenser isgenerally quite high, leading to high water costs and costs associatedwith wastewater treatment. Further, the water used in a typicalevaporative condenser refrigeration system, which is often chemicallytreated, can cause corrosion and degradation of the galvanized steelused in typical evaporative condensers. As such, a typical evaporativecondenser refrigeration system is expected to have a life span of onlyabout 15 years.

The air-cooled ammonia refrigeration system described herein uses anair-cooled condenser, also known as a “waterless condenser,” whereinminor amounts of water may be used to control head pressure, resultingin significantly reduced water costs and a higher life expectancy of thesystem. For example, in the air-cooled ammonia refrigeration systemdescribed herein, the air-cooled condensers are expected to last forabout 30 years, or even longer. In addition, because the air-cooledammonia refrigeration system described herein is configured tointermittently pulse atomized water to a surface of the air-cooledcondenser such that the water evaporates upon contact with the coils,wastewater costs associated with cooling the coils can be eliminated. Insome embodiments, the pulsed water may contain a water softening agent,which may prevent the spray nozzles from becoming clogged with mineraldeposits.

In some embodiments, the heat exchanger may comprise a finned tube heatexchanger, which may, in some embodiments, have a tube diameter of atleast about 0.5 inches and a fin density of at least about 12 fins perinch. This configuration allows for the reduction of temperature and/orpressure in the system compared to systems wherein the heat exchangercomprises tubes having a smaller diameter.

In some embodiments, the system may be configured such that theair-cooled condenser is elevated above a base surface, such as above aground surface or a roof surface, to allow for increased air flow belowthe air-cooled condensers. For example, the system may include aplurality of legs configured to elevate the heat exchanger above variousbase surfaces. In some embodiments, the plurality of legs is configuredto elevate the heat exchanger at least about 10 feet, and in someembodiments at least about 13 feet, above a roof surface. In someembodiments, the plurality of legs is configured to elevate the heatexchanger at least about 20 feet, and in some embodiments at least about25 feet, above a ground surface. Elevating the air-cooled condenser asdescribed above may reduce debris on the fin surface area, and may alsoimprove air flow and minimize heat being pulled from surrounding groundor roof surface, allowing cooler air to be drawn across the heatexchanger.

In some embodiments, the system may further include a high pressurereceiver coupled to the air-cooled condenser, and a recirculator coupledto the evaporator. In such a configuration, the high pressure receiverreceives the liquid ammonia from the air-cooled condenser, and therecirculator receives the liquid ammonia from the high pressure receiverthat has been cooled by the subcooler. In some embodiments, the highpressure receiver may also be coupled to the compressor such that thehigh pressure receiver provides liquid ammonia to cool the oil in theoil cooler that is coupled to the compressor.

As discussed above, previously, evaporative condensers were used inammonia refrigeration systems. However, such systems require highamounts of continuous water to cool the evaporative condensers, whichcan be costly to source, especially in geographic areas that are arid orareas that may be suffering from drought. These previous systems alsoproduce high amounts of wastewater, which can be costly to treat and/orto dispose of. The inventors of the present application designed asystem whereby an air-cooled condenser can be used in combination withan ammonia refrigeration system, resulting in significant cost savingscompared to previous ammonia refrigeration systems that used evaporativecondensers. FIG. 1 provides simplified diagram of an exemplaryair-cooled ammonia refrigeration system.

The system illustrated in FIG. 1 includes an air-cooled condenser 110configured to condense vaporous ammonia to form liquid ammonia.Exemplary air-cooled condensers that may be used in the system describedherein are illustrated in FIGS. 3 and 4. As shown in FIG. 3, theair-cooled condenser 110 includes a heat exchanger 102, which maycomprise any suitable heat exchanger for use in an air-cooled condenser.In some embodiments, the heat exchanger 102 in the air-cooled condenser110 may be a finned tube heat exchanger. The finned tube heat exchangermay be formed from any suitable material and may comprise any suitabledimensions for use in an air-cooled condenser. In some embodiments, thetubes of the heat exchanger may comprise stainless steel, while the finsof the heat exchanger may comprise aluminum. In some embodiments, thetubes of the finned tube heat exchanger may have a tube diameter of atleast about 0.5 inches, which allows for the reduction of temperatureand/or pressure in the system compared to systems wherein the heatexchanger comprises tubes having a smaller diameter. In someembodiments, the fins of the finned tube heat exchanger may have a findensity of at least about 12 fins per inch.

The air-cooled condenser 110 includes at least one axial fan 104, whichpulls cool air across the heat exchanger 102 to remove heat from thevaporous ammonia to form liquid ammonia. The air-cooled condenser 110may include any suitable number of axial fans 104. In some embodiments,the air-cooled condenser may include up to, for example, 12 axial fans,or in some embodiments, even more. The one or more axial fans 104 may becontrolled by a control circuit (an example of which is illustrated inFIG. 7 as control circuit 702) coupled to the one or more axial fans104. Previously, variable-frequency drives (VFD), which may becontrolled using a Programmable Logic Controller (PLC), have been usedto control various components or systems, such as fan motors, inconventional refrigeration systems. However, such control systems can beinefficient due to their lack of precision and/or insensitivity tochanging conditions. By contrast, the air-cooled ammonia refrigerationsystem described herein utilizes a control circuit to control the speedof the axial fan in response to one of more parameters. Such parametersmay include, for example, temperature, pressure (including subcoolingpressure), and the like.

Referring back to FIG. 1, the air-cooled condenser 110 is configured toflow vaporous ammonia through the heat exchanger 102, which condensesthe vaporous ammonia to form liquid ammonia. The system furthercomprises an evaporator 120 coupled to the air-cooled condenser andconfigured to evaporate liquid ammonia received from the air-cooledcondenser to form vaporous ammonia. A subcooler 130 is positionedbetween the air-cooled condenser 110 and the evaporator 120 and isconfigured to remove heat from the liquid ammonia passing from theair-cooled condenser 110 to the evaporator 120. The use of subcooler 130to reduce the temperature of the liquid ammonia advantageously reducesthe load on the system

The system further includes a compressor 140 coupled to the evaporator120 and is configured to compress the vaporous ammonia received from theevaporator 120. An oil cooler 150 is coupled to the compressor 140 andis configured to remove heat from circulating oil in the compressor 140.The oil cooler 150 used in the system described herein has a highercapacity than oil coolers used in conventional refrigeration systems. Insome embodiments, the circulating oil in the compressor 140 may comprisefully synthetic oil. Conventional oil coolers are designed for use withevaporative condenser refrigeration systems, which generally have lowercondensing temperature than air-cooled condensers. For example,conventional oil coolers that are used with evaporative condensersgenerally have a temperature limit of 95° F. The oil cooler 150 used inthe air-cooled ammonia refrigeration system described herein may beconfigured to have a higher temperature limit, such as, for example, atemperature limit of at least 105° F. Such a configuration allows forthe use of an air-cooled condenser, which generally runs hotter thanevaporative condensers, in an ammonia refrigeration system withoutlosing efficiency or shortening the life span of the compressor.

The system further includes a water system 160 coupled to the air-cooledcondenser 110, the water system comprising a water source 162, a waterpump 164, and a plurality of spray nozzles 166 positioned below theair-cooled condenser 110. An exemplary position of the spray nozzles 166with respect to the air-cooled condenser 110 is shown in FIG. 3. Inembodiments where the air-cooled condenser 110 comprises multiple axialfans 104, as illustrated in FIG. 4, a spray nozzle 166 may be positionedbeneath each axial fan 104. The spray nozzles 166 may be coupled to oneanother via a spray bar 168 positioned below the air-cooled condenser.

A control circuit (an example of which is illustrated in FIG. 7 ascontrol circuit 702) is coupled to the air-cooled condenser 110 and thewater system 160 and is configured to pulse atomized water through theplurality of spray nozzles 166 to a surface of the air-cooled condenser110 when a head pressure of the heat exchanger in the air-cooledcondenser 110 is higher than a predetermined value. Notably, the controlcircuit is configured to spray the atomized water in response to adetected head pressure, rather than in response to a detected in thetemperature of the system.

As discussed above, previously, variable-frequency drives (VFD), whichmay be controlled using a Programmable Logic Controller (PLC), have beenused to control various components or systems, such as a water spaysystem, in conventional refrigeration systems. However, such controlsystems can be inefficient due to their lack of precision and/orinsensitivity to changing conditions. The air-cooled ammoniarefrigeration system described herein utilizes a control circuit tocontrol the water system and its spray nozzles such that atomized wateris intermittently pulsed through the spray when the control circuitdetermines that the head pressure of the heat exchanger 102 of theair-cooled condenser 110 is higher than a predetermined value. In someembodiments, the control circuit is configured to pulse the atomizedwater such that the atomized water evaporates upon contact with thesurface of the air-cooled condenser 110 and no excess water is presenton the ground or on surrounding surfaces. Since the system pulsesatomized water only when the head pressure is high instead ofcontinuously spraying water, and the atomized water evaporates uponcontact with the surface of the heat exchanger, there is no wastewaterto treat and/or dispose of By contrast, previous ammonia refrigerationsystems use evaporative condensers, wherein the heat exchanger iscontinuously sprayed with water, resulting in high water and wastewatercosts. As a result of using the air-cooled ammonia refrigeration systemdescribed herein, the inventors surprisingly found that waterconsumption can be reduced by about 90%, in some embodiments by about95%, and in some embodiments by about 98%, over a 6 month period of usecompared to previous systems.

As discussed above, previous ammonia refrigeration systems that useevaporative condensers are expected to last only about 15 years, due tocorrosion of the heat exchanger, which is often made of steel coatedwith galvanized zinc. The air-cooled ammonia refrigeration systemdescribed herein is expected to last up to 30 years or more due, inpart, to the significant reduction in water used, treating the waterwith a softening agent, and/or using stainless steel to form componentsof the air-cooled condenser. In some embodiments, the atomized water maycontain a water softening agent, which may prevent the spray nozzlesfrom becoming clogged with mineral deposits.

FIG. 2 illustrates an exemplary air-cooled ammonia refrigeration systemthat is similar to the system shown in FIG. 1. As in FIG. 1, the systemshown in FIG. 2 includes an air-cooled condenser 110, an evaporator 120,a subcooler 130, a compressor 140, an oil cooler 150, and a water system160. These components in FIG. 2 may comprise the respective componentsdescribed above with reference to FIG. 1. The system may further includea high pressure receiver 170 coupled to the air-cooled condenser 110,and a recirculator 180 coupled to the evaporator 120. In such aconfiguration, the high pressure receiver 170 receives the liquidammonia from the air-cooled condenser 110, and the recirculator 180receives the liquid ammonia from the high pressure receiver 170 that hasbeen cooled by the subcooler 130. In some embodiments, the high pressurereceiver 170 may also be coupled to the compressor 140 such that thehigh pressure receiver provides liquid ammonia to cool the oil in theoil cooler 150 that is coupled to the compressor 140.

In some embodiments, the air-cooled refrigeration system described abovewith reference to FIGS. 1 and 2 may be configured or otherwise mountedin such a way so as to elevate one or more air-cooled condenser above abase surface, such as, for example, a ground surface or a roof surface.For example, in some embodiments, the system comprises a plurality oflegs configured to elevate the heat exchanger(s) of the one or moreair-cooled condensers at least about 10 feet from a base surface.Previously, air-cooled condensers were raised only a short distance fromthe base surface, such as, for example, about 3 feet from a groundsurface. In such a configuration, the fans in the condenser mayundesirable draw warm air from the surrounding ground over the heatexchanger, reducing the cooling efficiency of the condenser andincreasing energy costs. Elevating air-cooled condensers above a basesurface, in some embodiments at least about 10 feet above a basesurface, may reduce debris on the fin surface area and may also improveair flow and minimize heat being pulled from surrounding base surface,allowing cooler air to be drawn across the heat exchanger.

As illustrated in FIG. 5, the air-cooled refrigeration system describedabove with reference to FIGS. 1 and 2 may include a plurality of legs190 configured to elevate one or more air-cooled condensers 110 abovevarious surfaces. The air-cooled condensers 110 illustrated in FIG. 5may comprise the air-cooled condensers 110 described above withreference to FIGS. 1-4. For example, one or more air-cooled condensers110 may each comprise a heat exchanger and at least one axial fan, theair-cooled condensers being configured to condense vaporous ammonia toform liquid ammonia. In some embodiments, one or more air-cooledcondensers 110 may be elevated above, for example, a roof surface 500. Aroof surface may include the upper surface of any structure forming theupper covering of a building or dwelling 510, and may comprise anysuitable roofing material(s). In some embodiments, the roof surface 500may comprise a material that minimizes the possibility of warm air beingdrawn over the heat exchanger by the one or more axial fans of one ormore air-cooled condensers 110. In some embodiments, the roof surface500 itself may be at least about 25 feet, and in some embodiments atleast about 30 feet, above a ground surface 520. When one or moreair-cooled condensers 110 are mounted on a roof surface 500, a pluralityof legs 190 may elevate the heat exchanger(s) of the one or moreair-cooled condensers 110 at least about 10 feet, and in someembodiments at least about 13 feet, above the roof surface 500.

In some embodiments, as also shown in FIG. 5, one or more air-cooledcondensers 110 may be elevated above, for example, a ground surface 520.A ground surface may include any solid surface of the earth, includingany natural or synthetic material that generally conforms to the a solidsurface of the earth, such as, but not limited to, one or more of soil,grass, pavement, gravel, stone, brick, turf, wood, mulch, syntheticground covering, and the like. When one or more air-cooled condensers110 are mounted on a ground surface 520, a plurality of legs 190 mayelevate the heat exchanger(s) of the one or more air-cooled condensers110 at least about 20 feet, and in some embodiments at least about 25feet, above the ground surface 520.

It should be understood that although FIG. 5 illustrates multipleair-cooled condensers 110 being elevated above a roof surface 500 and aground surface 520 by a plurality of legs 190, similar configurationsmay be employed using a single air-cooled condenser 110 that isindividually elevated by a plurality of legs 190. Similarly, a pluralityof air-cooled condensers 110 may be individually elevated by a pluralityof legs 190.

Referring now to FIG. 6, a method of providing refrigeration using anair-cooled ammonia refrigeration system is shown. Generally, the method600 shown in FIG. 6 may be implemented with a processor based devicesuch as a control circuit, a central processor, and the like. In someembodiments, the method shown in FIG. 6 may be implemented by anair-cooled ammonia refrigeration system described above with referenceto FIGS. 1 and 2.

In step 610, vaporous ammonia is supplied to an air-cooled condensercomprising a heat exchanger and at least one axial fan. In someembodiments, the air-cooled condenser, heat exchanger, and axial fan maycomprise the air-cooled condenser 110, heat exchanger 102, and axial fan104 described above with reference to FIGS. 1-4. The air-cooledcondenser may include a heat exchanger, which may comprise any suitableheat exchanger for use in an air-cooled condenser. In some embodiments,the heat exchanger in the air-cooled condenser may be a finned tube heatexchanger. The finned tube heat exchanger may be formed from anysuitable material and may comprise any suitable dimensions for use in anair-cooled condenser. In some embodiments, the tubes of the heatexchanger may comprise stainless steel, while the fins of the heatexchanger may comprise aluminum. In some embodiments, the tubes of thefinned tube heat exchanger may have a tube diameter of at least about0.5 inches, which allows for the reduction of temperature and/orpressure in the system compared to systems wherein the heat exchangercomprises tubes having a smaller diameter. In some embodiments, the finsof the finned tube heat exchanger may have a fin density of at leastabout 12 fins per inch.

The air-cooled condenser may include at least one axial fan, which pullscool air across the heat exchanger to remove heat from the vaporousammonia to form liquid ammonia. The air-cooled condenser may include anysuitable number of axial fans. In some embodiments, the air-cooledcondenser may include up to, for example, 12 axial fans, or in someembodiments, even more. The one or more axial fans may be controlled bya control circuit coupled to the one or more axial fans. The controlcircuit may automatically control the speed of the axial fan in responseto one of more parameters. Such parameters may include, for example,temperature, pressure (subcooling pressure), and the like. The controlcircuit may comprise the control circuit 702 described below withreference to FIG. 7

In step 620, the vaporous ammonia is condensed to form liquid ammonia.The vaporous ammonia may condensed to form liquid ammonia using theair-cooled condenser described in step 610.

In step 630, heat is removed from the liquid ammonia. The heat may beremoved from the liquid ammonia by passing the liquid ammonia through asubcooler, which may comprise the subcooler 130 described above withreference to FIGS. 1 and 2. The use of a subcooler to reduce thetemperature of the liquid ammonia advantageously reduces the load on thesystem.

In step 640, the liquid ammonia is evaporated to form vaporous ammonia.The liquid ammonia may be evaporated to form vaporous ammonia by flowingthe liquid ammonia to an evaporator, which may comprise the evaporator120 described above with reference to FIGS. 1 and 2.

In step 650, atomized water is pulsed through a plurality of spraynozzles to a surface of the air-cooled condenser when a head pressure ofthe air-cooled condenser is higher than a predetermined value. In someembodiments, the atomized water may be pulsed using a water systemcomprising the water system described above with reference to FIGS. 1-4.For example, the water system may include a water source, a water pump,and a plurality of spray nozzles positioned below the air-cooledcondenser. In embodiments where the air-cooled condenser comprisesmultiple axial fans, a spray nozzle may be positioned beneath each axialfan. The spray nozzles may be coupled to one another via a spray barpositioned below the condenser.

A control circuit (an example of which is illustrated in FIG. 7 ascontrol circuit 702) may be coupled to the air-cooled condenser and thewater system and may be configured to pulse atomized water through theplurality of spray nozzles to a surface of the air-cooled condenser whena head pressure of the heat exchanger in the air-cooled condenser ishigher than a predetermined value. In some embodiments, the controlcircuit pulses the atomized water such that the atomized waterevaporates upon contact with the surface of the air-cooled condenser andno excess water is present on the ground or on surrounding surfaces.Since the system pulses atomized water only when the head pressure ishigh instead of continuously spraying water, and the atomized waterevaporates upon contact with the surface of the heat exchanger, there isno wastewater to treat and/or dispose of. By contrast, previous ammoniarefrigeration systems use evaporative condensers, wherein the heatexchanger is continuously sprayed with water, resulting in high waterand wastewater costs. As a result of using the air-cooled ammoniarefrigeration system described herein, the inventors surprisingly foundthat water consumption can be reduced by about 90%, in some embodimentsby about 95%, and in some embodiments by about 98%, over a 6 monthperiod of use compared to previous systems.

As discussed above, previous ammonia refrigeration systems that useevaporative condensers are expected to last only about 15 years, due tocorrosion of the heat exchanger, which is often made of steel coatedwith galvanized zinc. The air-cooled ammonia refrigeration systemdescribed herein is expected to last up to 30 years or more due, inpart, to the significant reduction in water used, treating the waterwith a softening agent, and/or using stainless steel to form componentsof the air-cooled condenser. In some embodiments, the atomized water maycontain a water softening agent, which may prevent the spray nozzlesfrom becoming clogged with mineral deposits.

In some embodiments, the method may further comprise flowing thevaporous ammonia to a compressor and compressing the vaporous ammonia,and flowing the vaporous ammonia back to the air-cooled condenser. Insome embodiments, the compressor may comprise the compressor 140described above with reference to FIGS. 1 and 2.

The method may further comprise removing heat from circulating oil inthe compressor. Heat may be removed from the circulating oil using, forexample, an oil cooler coupled to the compressor. In some embodiments,the oil cooler may comprise the oil cooler 150 described above withreference to FIGS. 1 and 2, which has a higher capacity than oil coolersused in conventional refrigeration systems. In some embodiments, thecirculating oil in the compressor may comprise fully synthetic oil. Asdiscussed above, conventional oil coolers are designed for use withevaporative condenser refrigeration systems, which generally have lowercondensing temperature than air-cooled condensers. For example,conventional oil coolers that are used with evaporative condensersgenerally have a temperature limit of 95° F. The oil cooler used in theair-cooled ammonia refrigeration system described herein may beconfigured to have a higher temperature limit, such as, for example, atemperature limit of at least 105° F. Such a configuration allows forthe use of an air-cooled condenser, which generally runs hotter thanevaporative condensers, in an ammonia refrigeration system withoutlosing efficiency or shortening the life span of the compressor.

In some embodiments, the liquid ammonia may be flowed from theair-cooled condenser to a high pressure receiver, from the high pressurereceiver to a recirculator via the subcooler, and from the recirculatorto the evaporator. The high pressure receiver and the recirculator maycomprise the high pressure receiver 170 and the recirculator 180described above with reference to FIG. 2. In some embodiments, liquidammonia may also be flowed from the high pressure receiver to thecompressor to cool the oil in the oil cooler that is coupled to thecompressor.

In some embodiments, one or more air-cooled condensers may be elevatedat least about 10 feet above various base surfaces, such as, forexample, a roof surface or a ground surface. A ground surface mayinclude any solid surface of the earth, including any natural orsynthetic material that generally conforms to the a solid surface of theearth, such as, but not limited to, one or more of soil, grass,pavement, gravel, stone, brick, turf, wood, mulch, synthetic groundcovering, and the like. A roof surface may include the upper surface ofany structure forming the upper covering of a building or dwelling, andmay comprise any suitable roofing material(s). In some embodiments, theroof surface may comprise a material that minimizes the possibility ofwarm air being drawn over the heat exchanger by the one or more axialfans of one or more air-cooled condensers. In some embodiments, the roofsurface itself may be at least about 25 feet, and in some embodiments atleast about 30 feet, above a ground surface.

When one or more air-cooled condensers are mounted on a roof surface, aplurality of legs may elevate the heat exchanger(s) of the one or moreair-cooled condensers at least about 10 feet, and in some embodiments atleast about 13 feet, above the roof surface. When one or more air-cooledcondensers are mounted on a ground surface, a plurality of legs mayelevate the heat exchanger(s) of the one or more air-cooled condensersat least about 20 feet, and in some embodiments at least about 25 feet,above the ground surface 520.

The methods, techniques, systems, devices, services, servers, sourcesand the like described herein may be utilized, implemented and/or run onmany different types of devices and/or systems. Referring to FIG. 7,there is illustrated an exemplary system 700 that may be used for anysuch implementations, in accordance with some embodiments. One or morecomponents of the system 700 may be used to implement any system,apparatus or device mentioned above or below, or parts of such systems,apparatuses or devices, such as for example, the air-cooled condenser110, the evaporator 120, the subcooler 130, the compressor 140, the oilcooler 150, the water system 160, the high pressure receiver 170, andthe recirculator 180, as described above with reference to FIGS. 1-6.

By way of example, the system 700 may include one or more system controlcircuits 702, memory 704, and input/output (I/O) interfaces and/ordevices 706. Some embodiments further include one or more userinterfaces 708. The system control circuit 702 typically comprises oneor more processors and/or microprocessors. The memory 704 stores theoperational code or set of instructions that is executed by the systemcontrol circuit 702 and/or processor to implement the functionality oneor more of the components listed above. In some embodiments, the memory704 may also store some or all of particular data that may be needed todetect and/or evaluate parameters such as, for example, temperature,pressure (including subcooling pressure), and the like. Such data may bepre-stored in the memory, received from an external source, bedetermined, and/or communicated to the system.

It is understood that the system control circuit 702 and/or processormay be implemented as one or more processor devices as are well known inthe art. Similarly, the memory 704 may be implemented as one or morememory devices as are well known in the art, such as one or moreprocessor readable and/or computer readable media and can includevolatile and/or nonvolatile media, such as RAM, ROM, EEPROM, flashmemory and/or other memory technology. Further, the memory 704 is shownas internal to the system 700; however, the memory 704 can be internal,external or a combination of internal and external memory. Additionally,the system typically includes a power supply (not shown), which may berechargeable, and/or it may receive power from an external source. WhileFIG. 7 illustrates the various components being coupled together via abus, it is understood that the various components may actually becoupled to the system control circuit 702 and/or one or more othercomponents directly.

Generally, the system control circuit 702 and/or electronic componentsof the system 700 can comprise fixed-purpose hard-wired platforms or cancomprise a partially or wholly programmable platform. Thesearchitectural options are well known and understood in the art andrequire no further description here. The system and/or system controlcircuit 702 can be configured (for example, by using correspondingprogramming as will be well understood by those skilled in the art) tocarry out one or more of the steps, actions, and/or functions describedherein. In some implementations, the system control circuit 702 and thememory 704 may be integrated together, such as in a microcontroller,application specification integrated circuit, field programmable gatearray or other such device, or may be separate devices coupled together.

The I/O interface 706 allows wired and/or wireless communicationcoupling of the system 700 to external components and/or or systems.Typically, the I/O interface 706 provides wired and/or wirelesscommunication (e.g., Wi-Fi, Bluetooth, cellular, RF, and/or other suchwireless communication), and may include any known wired and/or wirelessinterfacing device, circuit and/or connecting device, such as but notlimited to one or more transmitter, receiver, transceiver, etc.

The user interface 708 may be used for user input and/or output display.For example, the user interface 708 may include any known input devices,such one or more buttons, knobs, selectors, switches, keys, touch inputsurfaces, audio input, and/or displays, etc. Additionally, the userinterface 708 include one or more output display devices, such aslights, visual indicators, display screens, etc. to convey informationto a user, such as but not limited to item container quantityinformation, predefined location information, modification informationrelated to the modification and/or addition of predefined audiosignatures, status information, notifications, errors, conditions,and/or other such information. Similarly, the user interface 708 in someembodiments may include audio systems that can receive audio commands orrequests verbally issued by a user, and/or output audio content, alertsand the like.

In one embodiment, an air-cooled ammonia refrigeration system comprises:an air-cooled condenser comprising a heat exchanger and at least oneaxial fan, the air-cooled condenser configured to condense vaporousammonia to form liquid ammonia; an evaporator coupled to the air-cooledcondenser and configured to evaporate liquid ammonia received from theair-cooled condenser to form vaporous ammonia; a subcooler positionedbetween the air-cooled condenser and the evaporator and configured toremove heat from the liquid ammonia passing from the air-cooledcondenser to the evaporator; a compressor coupled to the evaporator andconfigured to compress the vaporous ammonia received from theevaporator; an oil cooler coupled to the compressor and configured toremove heat from circulating oil in the compressor; a water systemcoupled to the air-cooled condenser, the water system comprising a watersource, a water pump, and a plurality of spray nozzles positioned belowthe air-cooled condenser; and a control circuit coupled to theair-cooled condenser and the water system, the control circuitconfigured to pulse atomized water through the plurality of spraynozzles to a surface of the air-cooled condenser when a head pressure ofthe air-cooled condenser is higher than a predetermined value.

In one embodiment, method of providing refrigeration using air-cooledammonia refrigeration system comprises: supplying vaporous ammonia to anair-cooled condenser comprising a heat exchanger and at least one axialfan; condensing the vaporous ammonia to form liquid ammonia; removingheat from the liquid ammonia; evaporating the liquid ammonia to formvaporous ammonia; and pulsing atomized water through a plurality ofspray nozzles to a surface of the air-cooled condenser when a headpressure of the air-cooled condenser is higher than a predeterminedvalue.

In one embodiment, an air-cooled ammonia refrigeration system comprises:an air-cooled condenser comprising a finned tube heat exchanger having atube diameter of at least about 0.5 inches and a fin density of at leastabout 12 fins per inch, and at least one axial fan, the air-cooledcondenser configured to condense vaporous ammonia to form liquidammonia; an evaporator coupled to the air-cooled condenser andconfigured to evaporate liquid ammonia received from the air-cooledcondenser to form vaporous ammonia; a subcooler positioned between theair-cooled condenser and the evaporator and configured to remove heatfrom the liquid ammonia passing from the air-cooled condenser to theevaporator; a compressor coupled to the evaporator and configured tocompress the vaporous ammonia received from the evaporator; an oilcooler coupled to the compressor and configured to remove heat fromcirculating oil in the compressor; a water system coupled to theair-cooled condenser, the water system comprising a water source, awater pump, and a plurality of spray nozzles positioned below theair-cooled condenser; a control circuit coupled to the air-cooledcondenser and the water system, the control circuit configured to pulseatomized water through the plurality of spray nozzles to a surface ofthe air-cooled condenser when a head pressure of the air-cooledcondenser is higher than a predetermined value such that the atomizedwater evaporates upon contact with the surface of the air-cooledcondenser; and a plurality of legs configured to elevate the heatexchanger at least about 13 feet above a roof surface or at least about25 feet above a ground surface.

Those skilled in the art will recognize that a wide variety of othermodifications, alterations, and combinations can also be made withrespect to the above described embodiments without departing from thescope of the invention, and that such modifications, alterations, andcombinations are to be viewed as being within the ambit of the inventiveconcept.

What is claimed is:
 1. A system for controlling head pressure of anair-cooled condenser, the system comprising: an air-cooled condenserconfigured to condense vaporous ammonia to form liquid ammonia; a watersystem coupled to the air-cooled condenser, the water system comprisinga water source, a water pump, and a plurality of spray nozzles; and acontrol circuit coupled to the air-cooled condenser and the watersystem, the control circuit configured to: determine a head pressure ofthe air-cooled condenser; and when the head pressure of the air-cooledcondenser is higher than a predetermined value, provide atomized waterthrough the plurality of spray nozzles to a surface of the air-cooledcondenser such that the water evaporates upon contact with the surfaceof the air-cooled condenser.
 2. The system of claim 1, wherein none ofthe water provided to the surface of the air-cooled condenseraccumulates as wastewater.
 3. The system of claim 1, wherein the controlcircuit pulses the water through the plurality of spray nozzles to thesurface of the air-cooled condenser.
 4. The system of claim 1, whereinthe air-cooled condenser comprises a finned tube heat exchanger and atleast one fan.
 5. The system of claim 4, wherein the finned tube heatexchanger has a tube diameter of at least about 0.5 inches and a findensity of at least about 12 fins per inch.
 6. The system of claim 1,wherein a plurality of legs is configured to elevate the air-cooledcondenser at least about 13 feet above a roof surface.
 7. The system ofclaim 1, wherein a plurality of legs is configured to elevate theair-cooled condenser at least about 25 feet above a ground surface.
 8. Amethod of controlling head pressure of an air-cooled condenser, themethod comprising: providing an air-cooled condenser configured tocondense vaporous ammonia to form liquid ammonia; providing a watersystem coupled to the air-cooled condenser, the water system comprisinga water source, a water pump, and a plurality of spray nozzles;determining, using a control circuit, a head pressure of the air-cooledcondenser; and when the head pressure of the air-cooled condenser ishigher than a predetermined value, providing, using the control circuit,atomized water through the plurality of spray nozzles to a surface ofthe air-cooled condenser such that the water evaporates upon contactwith the surface of the air-cooled condenser.
 9. The method of claim 8,wherein none of the water provided to the surface of the air-cooledcondenser accumulates as wastewater.
 10. The method of claim 8, whereinthe water is pulsed through the plurality of spray nozzles to thesurface of the air-cooled condenser.
 11. The method of claim 8, whereinthe air-cooled condenser comprises a finned tube heat exchanger and atleast one fan.
 12. The method of claim 11, wherein the finned tube heatexchanger has a tube diameter of at least about 0.5 inches and a findensity of at least about 12 fins per inch.
 13. The method of claim 8,wherein a plurality of legs is configured to elevate the air-cooledcondenser at least about 13 feet above a roof surface.
 14. The method ofclaim 8, wherein a plurality of legs is configured to elevate theair-cooled condenser at least about 25 feet above a ground surface. 15.A system for controlling head pressure of an air-cooled condenser, thesystem comprising: an air-cooled condenser comprising a finned tube heatexchanger and at least one fan, the air-cooled condenser configured tocondense vaporous ammonia to form liquid ammonia; a water system coupledto the air-cooled condenser, the water system comprising a water source,a water pump, and a plurality of spray nozzles positioned adjacent theair-cooled condenser; and a control circuit coupled to the air-cooledcondenser and the water system, the control circuit configured to sprayatomized water through the plurality of spray nozzles to a surface ofthe air-cooled condenser when a head pressure of the air-cooledcondenser is higher than a predetermined value, wherein the waterevaporates upon contact with the surface of the air-cooled condenser.16. The system of claim 15, wherein none of the water provided to thesurface of the air-cooled condenser accumulates as wastewater.
 17. Thesystem of claim 15, wherein the control circuit pulses the water throughthe plurality of spray nozzles to the surface of the air-cooledcondenser.
 18. The system of claim 15, wherein the finned tube heatexchanger has a tube diameter of at least about 0.5 inches and a findensity of at least about 12 fins per inch.
 19. The system of claim 15,wherein a plurality of legs is configured to elevate the air-cooledcondenser at least about 13 feet above a roof surface.
 20. The system ofclaim 15, wherein a plurality of legs is configured to elevate theair-cooled condenser at least about 25 feet above a ground surface.